Biodegradable aliphatic-aromatic polyesters

ABSTRACT

Biodegradable aliphatic/aromatic copolyester comprising 50 to 60 mol % of an aromatic dicarboxylic acid and 40 to 50 mol % of an aliphatic acid, at least 90% of which is a long-chain dicarboxylic acid (LCDA) of natural origin selected from azelaic acid, sebacic acid, brassylic acid or mixtures thereof; and a diol component.

This application is a Divisional of U.S. application Ser. No.11/909,012, filed on Sep. 18, 2007, now U.S. Pat. No. 8,193,298 and forwhich priority is claimed under 35 U.S.C. §120; which is a NationalPhase filing under 35 U.S.C. §371 of PCT/EP2006/002670 filed on Mar. 17,2006, and claims priority of Application No. MI2005A000452 filed inItaly on Mar. 18, 2005, under 35 U.S.C. §119; the entire contents of allare hereby incorporated by reference.

The present invention relates to biodegradable aliphatic-aromaticpolyesters (AAPE) obtained from long-chain aliphatic dicarboxylic acids,polyfunctional aromatic acids and diols, as well as to mixtures of saidpolyesters with other biodegradable polymers of natural or syntheticorigin.

Biodegradable aliphatic-aromatic polyesters obtained from dicarboxylicacids and diols are known in the literature and are commerciallyavailable. The presence of the aromatic component in the polyester chainis important to obtain polymers with sufficiently high melting point andacceptable crystallization rate.

Although polyesters of this type are currently commercially available,the amount of aromatic acid in the chain is typically lower than 49%,since the percentage of biodegradation of the polyesters decreasessignificantly above said threshold.

It is reported in the literature (Muller et al., Angew. Chem., Int., Ed.(1999), 38, pp. 1438-1441) that copolymers of the polybutyleneadipate-co-terephthalate type with a molar fraction of terephthalate of42 mol %, biodegrade completely to form compost in twelve weeks, whereasproducts with 51 mol % of molar fraction of terephthalate show apercentage of biodegradation of less than 40%. This different behaviourwas attributed to the formation of a higher number of butyleneterephthalate sequences with a length greater than or equal to 3, whichare less easily biodegradable.

If it were possible to maintain suitable biodegradation properties, anincrease in the percentage of aromatic acid in the chain would, however,be desirable, in so far as it would bring about an increase in themelting point of the polyester, an increase in, or at least amaintenance of, important mechanical properties, such as ultimatestrength and elastic modulus, and would moreover bring about an increasein the crystallization rate of the polyester, thereby improving itsindustrial processability.

A further drawback of biodegradable aliphatic-aromatic polyesters thatare currently commercially available is represented by the fact that themonomers of which they are constituted come from non-renewable sources,thereby maintaining a significant environmental impact associated to theproduction of such polyesters, despite their biodegradability. They havefar more energy content than LDPE and HDPE, particularly in the presenceof adipic acid. On the other hand, the use of monomers of vegetal originwould contribute to the reduction of emission of CO₂ in the atmosphere,and to the reduction in the use of monomers derived from non-renewableresources.

U.S. Pat. No. 4,966,959 discloses certain copolyesters comprising from60 to 75% mol of terephtalic acid, 25 to 40% mol of a carboxylicaliphatic or cycloaliphatic acid, and a glycol component. The inherentviscosity of such polyesters is from about 0.4 to about 0.6, renderingthe polyesters useful as adhesives but unsuitable for many otherapplications.

U.S. Pat. No. 4,398,022 discloses copolyesters comprising terephtalicacid and 1,12-dodecanedioic acid and a glycol component comprising1,4-cyclohexanedimethanol. The acid component may optionally include oneor more acids conventionally used in the production of polyesters, butthe examples show that 1,12-dodecanedioic acid must be present for thepolyesters to have the desired melt strength.

U.S. Pat. No. 5,559,171 discloses binary blends of cellulose esters andaliphatic-aromatic copolyesters. The AAPE component of such blendscomprises a moiety derived from a C₂-C₁₄ aliphatic diacid which canrange from 30 to 95% mol in the copolymer, a moiety derived from anaromatic acid which can range from 70 to 5% mol in the copolymer.Certain AAPEs disclosed in this document do not require blending and areuseful in film application. They comprise a moiety derived from a C₂-C₁₀aliphatic diacid which can range from 95 to 35% mol in the copolymer,and a moiety derived from an aromatic acid which can range from 5 to 65%mol in the copolymer.

DE-A-195 08 737 discloses biodegradable AAPEs comprising terephtalicacid, an aliphatic diacid and a diol component. The weight averagemolecular weight M_(w) of such AAPEs is always very low (maximum 51000g/mol), so that their industrial applicability is limited.

It is therefore the overall object of the present invention to discloseimproved AAPEs and blends containing the same.

In fact, the present invention regards a biodegradablealiphatic/aromatic copolyester (AAPE) comprising:

A) an acid component comprising repeating units of:

-   -   1) 50 to 60 mol % of an aromatic polyfunctional acid;    -   2) 40 to 50 mol % of an aliphatic acid, at least 90% of which is        a long-chain dicarboxylic acid (LCDA) of natural origin selected        from azelaic acid, sebacic acid, brassylic acid or mixtures        thereof;

B) at least one diol component;

said aliphatic long-chain dicarboxylic acid (LCDA) and said diolcomponent (B) having a number of carbon atoms according to the followingformula:(C _(LCDA) ·y _(LCDA))/2+C _(B) ·y _(B)>7.5where:

-   -   C_(LCDA) is the number of carbon atoms of the LCDA and can be 9,        10 or 13;    -   y_(LCDA) is the molar fraction of each LCDA on the total number        of moles of LCDA;

C_(B) is the number of carbon atoms of each diol component;

y_(B) is the molar fraction of each diol on the total number of moles ofthe diol component (B)

said AAPE having:

-   -   a biodegradability after 90 days higher than 70%, with respect        to pure cellulose according to the Standard ISO 14855 Amendment        1;    -   a density equal to or less than 1.2 g/cc;    -   a number average molecular weight M_(n) of from 40,000 to        140,000;    -   an inherent viscosity of from 0.8 to 1.5

Preferably, the biodegradability after 90 days as defined above ishigher than 80%.

The AAPE according to the invention is rapidly crystallisable.

Preferably, the biodegradable polyesters of the invention arecharacterized in that said aliphatic long-chain dicarboxylic acid (LCDA)and said diol component (B) have a number of carbon atoms according tothe following formula:(C _(LCDA) ·y _(LCDA)/2)+C _(B) ·y _(B)>8

By “polyfunctional aromatic acids” for the purposes of the presentinvention are preferably meant aromatic dicarboxylic compounds of thephthalic-acid type and their esters, preferably terephthalic acid.

The content of aromatic dicarboxylic acid in the biodegradablepolyesters according to the present invention is between 50 mol % and 60mol % with respect to the total molar content of the dicarboxylic acids.

The number average molecular weight M_(n) of the polyester according tothe present invention is comprised between 40 000 and 140 000. Thepolydispersity index M_(w)/M_(n) determined by means of gel-permeationchromatography (GPC) is between 1.7 and 2.6, preferably between 1.8 and2.5.

Examples of diols according to the present invention are 1,2-ethandiol,1,2-propandiol, 1,3-propandiol, 1,4-butandiol, 1,5-pentandiol,1,6-hexandiol, 1,7-heptandiol, 1,8-octandiol, 1,9-nonandiol,1,10-decandiol, 1,11-undecandiol, 1,12-dodecandiol, 1,13-tridecandiol,1,4-cyclohexandimethanol, propylene glycol, neo-pentyl glycol,2-methyl-1,3-propandiol, dianhydrosorbitol, dianhydromannitol,dianhydroiditol, cyclohexandiol, and cyclohexan-methandiol.

Particularly preferred are diols of the C₂-C₁₀ type. Even moreparticularly preferred are the C₂-C₄ diols. Butandiol is the mostpreferred one.

The polyesters according to the invention have an inherent viscosity(measured with Ubbelhode viscosimeter for solutions in CHCl₃ of aconcentration of 0.2 g/dl at 25° C.) of between 0.8 dl/g and 1.5 dl/g,preferably between 0.83 dl/g and 1.3 dl/g and even more preferablybetween 0.85 dl/g and 1.2 dl/g.

The Melt Flow Rate (MFR) of the polyesters according to the invention,in the case of use for applications typical of plastic materials (suchas, for example, bubble filming, injection moulding, foams, etc.), isbetween 0.5 and 100 g/10 min, preferably between 1.5-70 g/10 min, morepreferably between 2.0 and 50 g/10 min (measurement made at 190° C./2.16kg according to the ASTM D1238 standard).

The polyesters according to the invention have a crystallizationtemperature T_(c) higher than 25° C., preferably higher than 30° C. andmost preferably higher than 40° C.

The polyesters have a density measured with a Mohr-Westphal weighingmachine equal to or less than 1.20 g/cm³.

The aliphatic acid A2 which can be different from LCDA can comprise orconsist of at least one hydroxy acid in an amount of up to 10 mol % withrespect to the total molar content of the aliphatic acid. Examples ofsuitable hydroxy acids are glycolic acid, hydroxybutyric acid,hydroxycaproic acid, hydroxyvaleric acid, 7-hydroxyheptanoic acid,8-hydroxycaproic acid, 9-hydroxynonanoic acid, lactic acid or lactide.The hydroxy acids can be inserted in the chain as such, or else can alsobe previously made to react with diacids or dialcohols. The hydroxy acidunits can be inserted randomly in the chain or can form blocks ofadjacent units.

In the process of preparation of the copolyester according to theinvention one or more polyfunctional molecules, in amounts of between0.02-3.0 mol %, preferably between 0.1 mol % and 2.5 mol % with respectto the amount of dicarboxylic acids (as well as to the possible hydroxyacids), can advantageously be added in order to obtain branchedproducts. Examples of these molecules are glycerol, pentaerythritol,trimethylol propane, citric acid, dipentaerythritol,monoanhydrosorbitol, monohydro-mannitol, epoxidized oils such asepoxidized soybean oil, epoxidized linseed oil and so on,dihydroxystearic acid, itaconic acid and so on.

Although the polymers according to the present invention reach highlevels of performance without any need to add chain extenders such as diand/or poly isocyanates and isocyanurates, di and/or poly epoxides,bis-oxazolines, poly carbodimides or divinylethers, it is in any casepossible to modify the properties thereof as the case may require.

Generally such additives are used in percentages comprised between0.05-2.5%, preferably 0.1-2.0%. In order to improve the reactivity ofsuch additives, specific catalysts can be used such as for example zincstearates (metal salts of fatty acids) for poly epoxides.

The increase in the molecular weight of the polyesters canadvantageously be obtained, for example, by addition of various organicperoxides during the process of extrusion. The increase in molecularweight of the biodegradable polyesters can be easily detected byobserving the increase in the values of viscosity following upontreatment of the polyesters with peroxides.

In case of use of the polyesters according to the present invention forthe production of films, the addition of the above mentioned chainextenders according to the teaching of EP 1 497 370 results in aproduction of a gel fraction lower than 4.5% w/w with respect to thepolyester. In this connection the content of EP 1 497 370 has to beintended as incorporated by reference in the present description.

The polyesters according to the invention possess properties and valuesof viscosity that render them suitable for use, by appropriatelyadjusting the molecular weight, in numerous practical applications, suchas films, injection-moulded products, extrusion-coating products,fibres, foams, thermoformed products, extruded profiles and sheets,extrusion blow molding, injection blow molding, rotomolding, stretchblow molding etc.

In case of films, production technologies like film blowing, casting,and coextrusion can be used. Moreover such films can be subject tobiorientation in line or after film production. The films can be alsooriented through stretching in one direction with a stretching ratiofrom 1:2 up to 1:15, more preferably from 1:2, 2 up to 1:8. It is alsopossible that the stretching is obtained in presence of an highly filledmaterial with inorganic fillers. In such a case, the stretching cangenerate microholes and the so obtained film can be particularlysuitable for hygiene applications.

In particular, the polyesters according to the invention are suitablefor the production of:

-   -   films, whether one-directional or two-directional, and        multilayer films with other polymeric materials;    -   films for use in the agricultural sector as mulching films;    -   cling films (extensible films) for foodstuffs, for bales in the        agricultural sector and for wrapping of refuse;    -   shrink film such as for example for pallets, mineral water, six        pack rings, and so on;    -   bags and liners for collection of organic matter, such as        collection of refuse from foodstuffs, and for gathering mowed        grass and yard waste;    -   thermoformed single-layer and multilayer packaging for        foodstuffs, such as for example containers for milk, yoghurt,        meat, beverages, etc.;    -   coatings obtained with the extrusion-coating technique;    -   multilayer laminates with layers of paper, plastic materials,        aluminium, metallized films;    -   foamed or foamable beads for the production of pieces formed by        sintering;    -   foamed and semi-foamed products including foamed blocks made up        of pre-foamed particles;    -   foamed sheets, thermoformed foamed sheets, containers obtained        therefrom for the packaging of foodstuffs;    -   containers in general for fruit and vegetables;    -   composites with gelatinized, destructured and/or complexed        starch, natural starch, flours, other fillers of natural,        vegetal or inorganic origin;    -   fibres, microfibres, composite fibres with a core constituted by        rigid polymers, such as PLA, PET, PTT, etc. and an external        shell made with the material according to the invention,        composite fibres, fibres with various sections (from round to        multilobed), flaked fibres, fabrics and non-woven fabrics or        spun-bonded or thermobonded fabrics for the sanitary sector, the        hygiene sector, the agricultural sector, georemediation,        landscaping and the clothing sector.

The polyesters according to the invention can moreover be used inblends, obtained also by reactive extrusion, whether with polyesters ofthe same type (such as aliphatic/aromatic copolyester as for examplepolybutylene tereptalate adipate PBTA, polybutylene tereftalatesuccinatePBTS, and polybutylene tereftalateglutarate PBTG) or with otherbiodegradable polyesters (for example, polylactic acid,poly-ε-caprolactone, polyhydroxybutyrates such aspoly-3-hydroxybutyrates, poly-4-hydroxybutyrates andpolyhydroxy-butyrate-valerate, polyhydroxybutyrate-propano-ate,polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decancate,polyhydroxybutyrate-dodecanoate, polyhydroxy-butyrate-hexadecancate,polyhydroxybutyrate-octadecanoate, and polyalkylene succinates and theircopolymers with adipic acid, lactic acid or lactide and caprolacton andtheir combinations), or other polymers different from polyesters.

Mixtures of polyesters with polylactic acid are particularly preferred.

According to another object of the invention, the polyesters accordingto the invention can also be used in blends with polymers of naturalorigin, such as for example starch, cellulose, chitosan, alginates,natural rubbers or natural fibers (such as for example jute, kenaf,hemp). The starches and celluloses can be modified, and amongst thesestarch or cellulose esters with a degree of substitution of between 0.2and 2.5, hydroxypropylated starches, and modified starches with fattychains may, for example, be mentioned. Preferred esters are acetates,propionates, butirrates and their combinations. Starch can moreover beused both in its destructurized form and in its gelatinized form or asfiller.

Mixtures of the AAPE according to the present invention with starch canform biodegradable polymeric compositions with good resistance to ageingand to humidity. In these compositions, which comprise thermoplasticstarch and a thermoplastic polymer incompatible with starch, starchconstitutes the dispersed phase and the AAPE thermoplastic polymerconstitutes the continuous phase.

The polymeric compositions can maintain a high tear strength even inconditions of low humidity. Such characteristic is obtained when starchis in the form of a dispersed phase with an average dimension lower than1 μm. The preferred average numeral size of the starch particles isbetween 0.1 and 0.5 microns and more than 80% of the particles have asize of less than 1 micron.

Such characteristics can be achieved when the water content of thecomposition during mixing of the components is preferably kept between 1and 15%. It is, however, also possible to operate with a content of lessthan 1% by weight, in this case, starting with predried andpre-plasticized starch.

It could be useful also to degrade starch at a low molecular weightbefore or during compounding with the polyesters of the presentinvention in order to have in the final material or finished product astarch inherent viscosity between 1 and 0.2 dl/g, preferably between 0.6and 0.25 dl/g, more preferably between 0.55 and 0.3 dl/g.

Destructurized starch can be obtained before of during mixing with thepolyesters of the present invention in presence of plasticizers such aswater, glycerol, di and polyglycerols, ethylene or propylene glycol,ethylene and propylene diglycol, polyethylene glycol,polypropylenglycol, 1,2 propandiol, trymethylol ethane, trimethylolpropane, pentaerytritol, dipentaerytritol, sorbitol, erytritol, xylitol,mannitol, sucrose, 1,3 propandiol, 1,2, 1,3, 1,4 buthandiol, 1,5pentandiol, 1,6, 1,5 hexandiol, 1,2,6, 1,3,5-hexantriol, neopenthilglycol, and polyvinyl alcohol prepolymers and polymers, polyolsacetates, ethoxylates and propoxylates, particularly sorbitolethoxylate, sorbitol acetate, and pentaerytritol acetate. The quantityof high boiling point plasticizers (plasticizers different from water)used are generally from 0 to 50%, preferably from 10 to 30% by weight,relative to starch.

Water can be used as a plasticizer in combination with high boilingpoint plasticizers or alone during the plastification phase of starchbefore or during the mixing of the composition and can be removed at theneeded level by degassing in one or more steps during extrusion. Uponcompletion of the plastification and mixing of the components, the wateris removed by degassing to give a final content of about 0.2-3% byweight.

Water, as well as high-boiling point plasticizers, modifies theviscosity of the starch phase and affects the rheological properties ofthe starch/polymer system, helping to determine the dimensions of thedispersed particles. Compatibilizers can be also added to the mixture.They can belong to the following classes:

-   -   Additives such as esters which have hydrophilic/lipophilic        balance index values (HLB) greater than 8 and which are obtained        from polyols and from mono or polycarboxylic acids with        dissociation constants pK lower than 4.5 (the value relates to        pK of the first carboxyl group in the case of polycarboxylic        acids.)    -   Esters with HLB values of between 5.5 and 8, obtained from        polyols and from mono or polycarboxylic acids with less than 12        carbon atoms and with pK values greater than 4.5 (this value        relates to the pK of the first carboxylic group in the case of        polycarboxylic acids).    -   Esters with HLB values lower than 5.5 obtained from polyols and        from fatty acids with 12-22 carbon atoms.

These compatibilizers can be used in quantities of from 0.2 to 40%weight and preferably from 1 to 20% by weight related to the starch. Thestarch blends can also contain polymeric compatibilizing agents havingtwo components: one compatible or soluble with starch and a second onesoluble or compatible with the polyester.

Examples are starch/polyester copolymers through transesterificationcatalysts. Such polymers can be generated trough reactive blendingduring compounding or can be produced in a separate process and thenadded during extrusion. In general block copolymers of an hydrophilicand an hydrophobic units are particularly suitable.

Additives such as di and polyepoxides, di and poly isocyanates,isocyanurates, polycarbodiimmides and peroxides can also be added. Theycan work as stabilizers as well as chain extenders.

All the products above can help to create the needed microstructure.

It is also possible to promote in situ reactions to create bonds betweenstarch and the polymeric matrix. Also aliphatic-aromatic polymers chainextended with aliphatic or aromatic diisocyanates or di and polyepoxidesor isocyanurates or with oxazolines with intrinsic viscosities higherthan 1 dl/g or in any case aliphatic-aromatic polyesters with a ratiobetween Mn and MFI at 190° C., 2.16 kg higher than 10 000, preferablyhigher than 12 500 and more preferably higher than 15 000 can also beused to achieve the needed microstructure.

Another method to improve the microstructure is to achieve starchcomplexation in the starch-polyester mixture.

In such a case, in the X-Ray spectra of the compositions with thepolyester according to the present invention the He/Ha ratio between theheight of the peak (He) in the range of 13-14° of the complex and theheight of the peak (Ha) of the amorphous starch which appears at about20.5° (the profile of the peak in the amorphous phase having beenreconstructed) is less than 2 and greater than 0.02.

The starch/polyester ratio is comprised in the range 5/95% weight up to60/40% by weight, more preferably 10/90-45/55% by weight.

In such starch-based blends in combination with the polyesters of thepresent invention it is possible to add polyolefins, polyvynil alcoholat high and low hydrolysis degree, ethylene vinylalcohol and ethylenevinylacetate copolymers and their combinations as well as aliphaticpolyesters such as polybuthylensuccinate, polybuthylensuccinate adipate,polybuthylensuccinate adipate-caprolactate,polybuthylensuccinate-lactate, polycaprolactone polymers and copolymers,PBT, PET, PTT, polyamides, polybuthylen terephtalate adipates with acontent of terephtalic acid between 40 and 70% with and withoutsolfonated groups with or without branchs and possibly chain extendedwith diisocianates or isocianurates, polyurethanes, polyamide-urethanes,cellulose and starch esters such as acetate, propionate and butyrratewith substitution degrees between 1 and 3 and preferably between 1.5 and2.5, polyhydroxyalkanoates, poly L-lactic acid, poly-D lactic acid andlactides, their mixtures and copolymers.

The starch blends of the polyesters of the present invention maintain abetter ability to crystallize in comparison with compostable starchblends where copolyester are polybuthylen adipate terephtalates atterephtalic content between 45 and 49% (range of the product withindustrial performances) and can be easily processable in film blowingeven at MFI (170° C., 5 kg) of 7 g/10 min due to the highcrystallization rate of the matrix. Moreover they have impact strengthhigher than 20 kj/m2, preferably higher than 30 kj/m2 and mostpreferably higher than 45 kj/m2 (measured on blown film 30 um thick at10° C. and less then 5% relative humidity).

Particularly resistant and easily processable compounds containdestructurized starch in combination with the polyesters of theinvention and polylactic acid polymers and copolymers with and withoutadditives such as polyepoxydes, carbodiimmides and/or peroxides.

The starch-base films can be even transparent in case of nanoparticlesof starch with dimensions lower than 500 μm and preferably lower than300 μm.

It is also possible to go from a dispersion of starch in form ofdroplets to a dispersion in which two co-continuous phases coexist andthe blend is characterized for allowing a higher water content duringprocessing.

In general, to obtain co-continuous structures it is possible to workeither on the selection of starch with high amylopectine content and/orto add to the starch-polyester compositions block copolymers withhydrophobic and hydrophilic units. Possible examples arepolyvynilacetate/polyvinylalcohol and polyester/polyether copolymers inwhich the block length, the balance between the hydrophilicity andhydrophobicity of the blocks and the quality of compatibilizer used canbe suitably changed in order to finely adjust the microstructure of thestarch-polyester compositions.

The polyesters according to the invention can also be used in blendswith the polymers of synthetic origin and polymers of natural originmentioned above. Mixtures of polyesters with starch and polylactic acidare particularly preferred.

Blends of the polyesters according the present invention with PLA are ofparticular interest because the high crystallization rate of thealiphatic-aromatic polyesters of the invention and their highcompatibility with PLA polymers and copolymers permits to covermaterials with a wide range of rigidities and high speed ofcrystallization which makes these blends particularly suitable forinjection molding and extrusion.

Moreover, blends of such polyesters with poly L-lactic acid and polyD-lactic acid or poly L-lactide and D-lactide where the ratio betweenpoly L- and poly D-lactic acid or lactide is in the range 10/90-90/10,preferably 20/80-80/20, and the ratio between aliphatic-aromaticpolyester and the polylactic acid or PLA blend is in the range5/95-95/5, preferably 10/90-90/10, are of particular interest for thehigh crystallization speed and the high thermal resistance. Polylacticacid or lactide polymers or copolymers are generally of molecular weightMn in the range between 30 000 and 300 000, more preferably between 50000 and 250 000.

To improve the transparency and thoughness of such blends and decreaseor avoid a lamellar structure of polylactide polymers, it is possible tointroduce other polymers as compatibilizers or toughening agents suchas: polybuthylene succinate and copolymers with adipic acid and orlactic acid and or hydroxyl caproic acid, polycaprolactone, aliphaticpolymers of diols from C2 to C13 and diacids from C4 to C13,polyhydroxyalkanoates, polyvynilalcohol in the range of hydrolysisdegree between 75 and 99% and its copolymers, polyvynilacetate in arange of hydrolysis degree between 0 and 70%, preferably between 0 and60%. Particularly preferred as diols are ethylene glycol, propandiol,butandiol and as acids: azelaic, sebacic, undecandioic acid,dodecandioic acid, brassylic acid and their combinations.

To maximize compatibility among the polyesters of the invention andpolylactic acid it is very useful the introduction of copolymers withblocks having high affinity for the aliphatic-aromatic copolyesters ofthe invention, and blocks with affinity for the lactic acid polymers orcopolymers. Particularly preferred examples are block copolymers of thealiphatic aromatic copolymers of the invention with polylactic acid.Such block copolymers can be obtained taking the two original polymersterminated with hydroxyl groups and then reacting such polymers withchain extenders able to react with hydroxyl groups such asdiisocyanates. Examples are 1,6 esamethylendiisocyanate,isophorondiisocyanate, methylendiphenildiisocyanate, toluendiisocyanateor the like. It is also possible to use chain extenders able to reactwith acid groups like di and poly epoxides (e.g. bisphenols diglycidylethers, glycerol diglycidyl ethers) divinyl derivatives if the polymersof the blend are terminated with acid groups. It is possible also to useas chain extenders carbodiimmides, bis-oxazolines, isocyanurates etc.

The intrinsic viscosity of such block copolymers can be between 0.3 and1.5 dl/g, more preferably between 0.45 and 1.2 dl/g. The amount ofcompatibilizer in the blend of aliphatic-aromatic copolyesters andpolylactic acid can be in the range between 0.5 and 50%, more preferablybetween 1 and 30%, more preferably between 2 and 20% by weight.

The polyesters according to the present invention can advantageously beblended also with filler both of organic and inorganic nature. Thepreferred amount of fillers is in the range of 0.5-70% by weight,preferably 5-50% by weight.

As regards organic fillers, wood powder, proteins, cellulose powder,grape residue, bran, maize husks, compost, other natural fibres, cerealgrits with and without plasticizers such as polyols can be mentioned.

As regards inorganic fillers, it can be mentioned substances that areable to be dispersed and/or to be reduced in lamellas with submicronicdimensions, preferably less than 500 nm, more preferably less than 300nm, and even more preferably less than 50 nm. Particularly preferred arezeolites and silicates of various kind such as wollastonites,montmorillonites, hydrotalcites also functionalised with molecules ableto interact with starch and or the specific polyester. The use of suchfillers can improve stiffness, water and gas permeability, dimensionalstability and maintain transparency.

The process of production of the polyesters according to the presentinvention can be carried out according to any of the processes known tothe state of the art. In particular the polyesters can be advantageouslyobtained with a polycondensation reaction.

Advantageously, the process of polymerization of the copolyester can beconducted in the presence of a suitable catalyst. As suitable catalysts,there may be mentioned, by way of example, metallo-organic compounds oftin, for example derivatives of stannoic acid, titanium compounds, forexample orthobutyl titanate, and aluminium compounds, for exampletriisopropyl aluminium, antimony compounds, and zinc compounds.

EXAMPLES

In the examples provided hereinafter, the following test methods wereadopted:

-   -   MFR was measured in the conditions envisaged by the ASTM D        1238-89 standard at 150° C. and 5 kg or at 190° C. and 2.16 kg;    -   the melting and crystallization temperatures and enthalpies were        measured with a differential scanning calorimeter Perkin Elmer        DSC7, operating with the following thermo profile:        -   1st scan from −30° C. to 200° C. at 20° C./min        -   2nd scan from 200° C. to −30° C. at 10° C./min        -   3rd scan from −30° C. to 200° C. at 20° C./min    -   T_(m1) was measured as endothermic-peak value of the 1st scan,        and T_(m2) as that of the 3rd scan; T_(c) was measured as        exothermic-peak value of the 2nd scan.

Density

Determination of Density according to the Mohr Westphal method wasperformed with an analytical balance Sartorius AC 120S equipped with aSartorius Kit YDK 01. The Kit was provided with two small baskets. Oncethe Kit had been mounted, ethanol was introduced in the crystallizer.The balance was maintained at room temperature.

Each test was performed with about 2 g of polymer (one or more pellets).

The density d was determined according to the formula below:D=(W _(a) /G)d _(f1)whereW_(a): weight of the sample in airW_(f1): weight of the sample in alcoholG=W _(a) −W _(f1)d_(f1)=ethanol density at room temperature (Values read on tablesprovided by the company Sartorius with the Kit).

The experimental error of the Density values was in the range of±2.5×10⁻³.

-   -   η_(in) has been determined according to the ASTM 2857-87 method    -   M_(n) has been determined on a Agilent 1100 Series GPC system,        with chloroform as eluent and polystyrene standards for the        calibration curve”.

Example 1

A 25-l steel reactor, provided with a mechanical stirrer, an inlet forthe nitrogen flow, a condenser, and a connection to a vacuum pump wascharged with:

-   -   2890 g of terephthalic acid (17.4 mol),    -   3000 g of sebacic acid (14.8 mol),    -   3500 g butandiol (38.9 mol),    -   6.1 g of butylstannoic acid.

The molar percentage of terephthalic acid with respect to the sum of themoles of the acid components was 54.0 mol %.

The temperature of the reactor was then increased up to 200° C., and anitrogen flow was applied. After approximately 90% of the theoreticalamount of water had been distilled, the pressure was gradually reducedto a value of less than 3 mmHg, and the temperature was raised to 240°C.

After approximately 3 hours, the molten product was poured from thereactor, cooled in a water bath and granulated. During the latteroperations it was possible to note how the product starts to solidifyrapidly and can be easily granulated. The product obtained had aninherent viscosity (measured in chloroform at 25° C., c=0.2 g/dl)η_(in)=0.93 (dl/g), MFR (190° C., 2.16 kg)=20 g/10 min, M_(n)=52103 anda density of 1.18 g/cm³.

From H-NMR analysis a percentage of aromatic units was found of53.5±0.5%.

Example 1A

The reactor as per Example 1 was charged with the same ingredients ofExample 1:

-   -   2890 g of terephthalic acid (17.4 mol),    -   3000 g of sebacic acid (14.8 mol),    -   3500 g butandiol (38.9 mol),    -   6.1 g of butylstannoic acid.

The molar percentage of terephthalic acid with respect to the sum of themoles of the acid components was 54.0 mol %.

The reaction has been carried out for the time necessary to obtain aproduct having an inherent viscosity (measured in chloroform at 25° C.,c=0.2 g/dl) η_(in)=1.03 (dl/g), MFR (190° C.; 2.16 kg)=14.8 g/10 min,M_(n)=58097 and a density of 1.18 g/cm³.

Example 2 Comparison

The reactor as per Example 1 was charged with:

-   -   2480 g of terephthalic acid (14.9 mol),    -   3400 g of sebacic acid (16.8 mol),    -   3430 g butandiol (38.1 mol),    -   6.1 g of butylstannoic acid.

The molar percentage of terephthalic acid with respect to the sum of themoles of the acid components was 47 mol %.

The temperature of the reactor was then raised to 200° C., and anitrogen flow was applied. After approximately 90% of the theoreticalamount of water had been distilled, the pressure was reduced graduallyuntil a value of less than 3 mmHg was reached, and the temperature wasraised up to 240° C.

After approximately 3 hours, a product was obtained with inherentviscosity (measured in chloroform at 25° C., c=0.2 g/dl) η_(in)=1.00(dl/g) and MFR (190° C.; 2.16 kg)=13 g/10 min.

From H-NMR analysis, a percentage of aromatic units of 47.0±0.5% wasfound.

Example 3 Comparison

The reactor as per Example 1 was charged with:

-   -   2770 g of dimethyl terephthalate (14.3 mol),    -   3030 g of dimethyl adipate (17.4 mol),    -   3710 g of butandiol (41.2 mol),    -   0.7 g of tetraisopropyl orthotitanate (dissolved in n-butanol)

The molar percentage of aromatic content with respect to the sum of themoles of the acid components was 45 mol %.

The temperature of the reactor was then increased to 200-210° C.

After at least 95% of the theoretical amount of methanol had beendistilled, the pressure was gradually reduced until a value of less than2 mmHg was reached, and the temperature was raised to 250-260° C.

After approximately 4 hours, a product was obtained with inherentviscosity (measured in chloroform at 25° C., c=0.2 g/dl) η_(in)=0.92(dl/g) and MFR (190° C.; 2.16 kg)=20 g/10 min.

From H-NMR analysis, a percentage of aromatic units of 47.0±0.5% wasfound.

Example 4 Comparison

The process of Example 1 was repeated with:

-   -   3623.9 g of dimethyl terephthalate (18.68 mol),    -   3582.5 g of butandiol (39.81 mol),    -   2244.7 g of azelaic acid (11.94 mol).

The molar percentage of aromatic content with respect to the sum of themoles of the acid components was 61 mol %.

A product was obtained with inherent viscosity (measured in chloroformat 25° C., c=0.2 g/dl) η_(in)=0.95 (dl/g), density 1.21 g/cc and MFR(190° C., 2.16 kg)=5.5 g/10 min.

Example 5

The process of Example 1 was repeated with:

-   -   3476.48 g of dimethyl terephthalate (17.92 mol),    -   3493.80 g of butandiol (38.82 mol),    -   2411 g of sebacic acid (11.94 mol).

The molar percentage of aromatic content with respect to the sum of themoles of the acid components was 60 mol %.

A product was obtained with M_(n)=56613, M_(w)/M_(n)=2.0364 inherentviscosity (measured in chloroform at 25° C., c=0.2 g/dl) η_(in)=0.97(dl/g), density 120 g/cc and MFR (190° C.; 2.16 kg)=7.8 g/10 min.

Example 6

The process of Example 1 was repeated with:

-   -   3187.4 g of dimethyl terephthalate (16.43 mol),    -   3559.1 g of butandiol (39.55 mol),    -   2630.1 g of azelaic acid (14.00 mol).

The molar percentage of aromatic content with respect to the sum of themoles of the acid components was 54 mol %.

A product was obtained with inherent viscosity (measured in chloroformat 25° C., c=0.2 g/dl) η_(in)=1.04 (dl/g), density=1.2 g/cc and MFR(190° C.; 2.16 kg)=7.12 g/10 min.

Example 7

The process of Example 1 was repeated with:

-   -   2865.4 g of dimethyl terephthalate (14.77 mol),    -   3201.1 g of butandiol (35.57 mol),    -   3072 g of brassylic acid (12.6 mol).

The molar percentage of aromatic content with respect to the sum of themoles of the acid components was 54 mol %.

A product was obtained with inherent viscosity (measured in chloroformat 25° C., c=0.2 g/dl) η_(in)=0.90 (dl/g), density=1.16 g/cc and MFR(190° C.; 2.16 kg)=g/10 min.

The specimens of the above examples were then filmed with the blow-filmtechnique, on a Formac Polyfilm 20 apparatus, equipped with meteringscrew 20C13, L/D=25, RC=1.3; air gap 1 mm; 30-50 RPM; T=140-180° C. Thefilms thus obtained had a thickness of approximately 30 μm.

A week after filming, and after conditioning at 23(?)° C., with 55%relative humidity, the tensile properties were measured according to theASTM D882-88 standards.

Listed in Table 1 are the thermal properties of the products of theexamples, whilst Table 2 lists the mechanical properties of the filmsobtained from such products.

TABLE 1 Thermal properties Example Aromatic T_(m1) ΔH_(m1) T_(c) ΔH_(c)T_(m2) 1 53.5%  133 28 58 20 130 1A 53.5 — — 46 19 129 2 (comp.) 47% 11219 22 19 113 3 (comp.) 47% 120 19 16 18 114 4 (comp) 61% — — 104 21 1545 60% — — 82 23 145 6 54% — — 42 24 130 7 54% — — 76 16 133

TABLE 2 Mechanical properties Tensile EXAMPLE properties - 2 3 4longitudinal 1 (comp) (comp) (comp) 5 6 7* Yield point 11 6.5 9 11.5 129 6 (MPa) Ultimate 40 28 40 40.0 45 33.5 23.5 strength (MPa) Elastic 9065 105 170 130 120 70 modulus (MPa) Failure energy 143 135 170 150 154169 155 (MJ/m³) *The mechanical properties of the product of example 7were tested on a compression molded sample with a thickness of about 100μm.

Biodegradation Test

For the products of Table 3 the biodegradation test was carried out incontrolled composting according to the Standard ISO 14855 Amendment 1.

The tests were carried out on 30-micron films ground in liquid nitrogenuntil they were fragmented to a size of less than 2 mm, or on pelletsground to particles having diameter<250 μm. As positive controlmicrocrystalline cellulose Avicel® for column chromatography lot No.K29865731 202 was used. Powder grain size: 80% between 20 μm and 160 μm;20% less than 20 μm.

TABLE 3 BIODEGRADATION Particles Relative Aromatic LCDA/ groundbiodegradation Example content Diol from after 90 days 1 53.5%   SebacicFilm 107.44 Butandiol 2 (comp.) 47% Sebacic Film 99.6 Butandiol 3(comp.) 47% Adipic Film 80.71 Butandiol Cellulose — — Film/ 100 pellets4 (comp.) 61% Azelaic pellets 10.39 Butandiol (end of the test: 49 days)5 60% Sebacic pellets 104 Butandiol 6 54% Azelaic pellets 82 Butandiol 754% Brassilic pellets 73 Butandiol

TABLE 4 DENSITY Aromatic Density Example content LCDA/Diol g/cc 153.5%   Sebacic/Butandiol 1.18 2 (comp.) 47 Sebacic/Butandiol 1.17 3(comp.) 47% Adipic/Butandiol 1.23 4 (comp.) 61% Azelaic/Butandiol 1.21 560% Sebacic/Butandiol 1.20 6 54% Azelaic/Butandiol 1.20 7 54%Brassylic/Butandiol 1.15

It appears from the examples above that the selection of AAPEs accordingto the present invention provides products having an excellent balanceof biodegradability and mechanical properties.

Example 8

28 parts by weight of the polymer of example 6 were blended with 58parts of poly L-lactide polymer having a Mn of 180000, MFR at 190° C.,2.16 kg of 3.5 g/10 min, a residue of lactide less than 0.2% and a Dcontent of about 6%, and 14 parts of talc. The extruder used was a twinscrew extruder Haake Rheocord 90 Rheomex TW-100. The thermal profile wasranging between 120 and 190° C.

The pellets obtained have been dried for 1 hour at 60 C. The meltviscosity was of 600 Pa*s, measured at 190° C. and shear rate of 100sec-1 in a capillary rheometer Goettfert Rheotester 1000 equipped with acapillary rheometer of 1 mm. The pellets have been injection molded in aSandretto Press 60 Series 7 using a dumbbell mold for the production ofsamples for mechanical testing and a 12 cavity clipper mold to test theindustrial moldability.

The mechanical properties obtained on dumbbell samples according to theASTM norm D638, after conditioning at 23° C., 55% RH are reported below:

Stress at break (MPa) 42

Elongation at break (%) 271

Young Modulus (MPa) 2103

Energy at break (Kj/m2) 1642

The dumbbell samples have been tested in biodegradation under controlledcomposting obtaining 100% of biodegradation in 50 days. The processingcycles are comparable to polypropilene and are of 14 seconds and themolding system is perfectly automatic.

A blend different from the one described in this example just for thearomatic-aliphatic polyester, particularly the polymer of example 6 isreplaced with poly buthylen adipate terephtalate MFR 3.4 at 190° C.,2.16 kg, terephtalic acid 47% mole and density of 1.23 g/cm3 the moldedparts could not be demolded automatically.

Example 9

A blend has been made mixing 70% by weight of the polymer of example 5and 30% by weight of the same PLA described in example 8. The blend hasbeen produced in the twin screw extruder of example 8 with the samethermal profile. The pellets have been dried and have been film blown asreported in the previous examples.

The film has shown the following tensile performances in the filmdirection:

-   -   Stress at break (MPa) 25    -   Elongation at break (%) 400    -   Young Modulus (MPa) 590    -   Energy at break (Kj/m2) 3600

The film had a good transparency. The tear strength was different in thetwo directions of film blowing showing a significant orientation.

The addition of 10% of a block copolymer of PLA and an aliphaticaromatic block constituted by butandiol with sebacic and terephtalicacid in a ratio 46-54% by mole, having 0.85 dl/g of viscosity gavetensile properties similar and better than the sample withoutcompatibilizer (Stress at break (MPa) 28, Elongation at break (%) 380,Young Modulus (MPa) 840, Energy at break (Kj/m2) 3600) but the tearstrength was more balanced in the two directions.

What is claimed is:
 1. Polymeric composition comprising A) abiodegradable aliphatic/aromatic copolyester (AAPE) comprising: a) anacid component comprising repeating units of: 50 to 60% of an aromaticpolyfunctional acid; 40 to 50% of an aliphatic acid, at least 90% ofwhich is a long-chain dicarboxylic acid (LCDA) of natural originselected from azelaic acid, sebacic acid, brassylic acid or mixturesthereof; b) at least one diol component; said aliphatic long-chaindicarboxylic acid (LCDA) and said diol component (b) having a number ofcarbon atoms according to the following formula:(CLCDA*YLCDA)/2+CB·YB>7.5 where: CLCDA is the number of carbon atoms ofthe LCDA and can be 9, 10 or 13; YLCDA is the molar fraction of eachLCDA on the total number of moles of LCDA; Cb is the number of carbonatoms of each diol component; Yb is the molar fraction of each diol onthe total number of moles of the diol component (b) said AAPE having: abiodegradability after 90 days higher than 70%, with respect to purecellulose according to the Standard ISO 14855 Amendment 1; a density ofequal to or less than 1.2 glee; a number average molecular weight Mn of40,000-140,000; an inherent viscosity of 0.8-1.5; and B) at least oneother polymer selected from other polyesters of the aliphatic/aromatictype or biodegradable polymers of natural origin or of synthetic origin.2. Polymeric composition according to claim 1, wherein the diol of thealiphatic/aromatic copolyester (A) is selected from the group consistingof: 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol,1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol,1,13-tridecanediol, 1,4-cyclohexanedimethanol, propylene glycol,neo-pentyl glycol, 2-methyl-1,3-propanediol, dianhydrosorbitol,dianhydromannitol, dianhydroiditol cyclohexanediol, andcyclohexanemethanediol.
 3. Polymeric composition according to claim 2,wherein said diol has from 2 to 10 carbon atoms.
 4. Polymericcomposition according to claim 3, wherein said diol has from 2 to 4carbon atoms.
 5. Polymeric composition according to claim 1, wherein thearomatic polyfunctional acid of the aliphatic/aromatic copolyester (A)is selected from the group consisting of the phthalic acids. 6.Polymeric composition according to claim 1, wherein said biodegradablealiphatic/aromatic copolyester (A) further comprises one or morepolyfunctional molecules in amounts of between 0.02-3.0 mol % withrespect to the amount of dicarboxylic acids.
 7. Polymeric compositionaccording to claim 1, wherein the aliphatic acid of the biodegradablealiphatic/aromatic copolyester (A) further comprises at least onehydroxyl acid in an amount of up to 10 mol % with respect to the totalmolar content of the aliphatic acid.
 8. Polymeric composition accordingto claim 1, wherein the aliphatic long-chain dicarboxylic acid (LCDA)and the diol component (b) of the biodegradable aliphatic/aromaticcopolyester (A) have a number of carbon atoms according to the followingformula:(CLCDA*YLCDA)/2+CB·YB>8.
 9. Polymeric composition according to claim 1wherein said at least one other polymer (B) is a polymer of syntheticorigin selected from the group consisting of polylactic acid,poly-ε-caprolactone, polyhydroxybutyrates, such aspolyhydroxybutyrate-valerate, polyhydroxybutyrate propanoate,polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decanoate,polyhydroxybutyrate-dodecanoate, polyhydroxybutyrate-hexadecanoate,polyhydroxybutyrate-octadecanoate, and polyalkylene succinates. 10.Polymeric composition according to claim 1, wherein said at least oneother polymer (B) is a polymer of natural origin selected from the groupconsisting of starch, cellulose, chitosan, alginates or natural rubbers.11. Polymeric composition according to claim 10, wherein said starch orcellulose is modified.
 12. Polymeric composition according to claim 11,wherein the modified starch or celluloses are starch or cellulose esterswith a degree of substitution of between 0.2 and 2.5, hydroxypropylatedstarches, and modified starches with fatty chains.
 13. Polymericcomposition according to claim 10, wherein the starch is present in adestructurized or gelatinized form or in the form of fillers. 14.Polymeric composition according to claim 1, wherein the starch ispresent in the form of a dispersed phase with an average dimension lowerthan 1 micron.
 15. Polymeric composition according to claim 1, in whichthe polymer of synthetic origin is polylactic acid and the polymer ofnatural origin is starch.
 16. Polymeric composition according to claim1, comprising chain extenders, in a quantity comprised between 0.05-2.5wt. %.
 17. A method for the production of at least one member selectedfrom the group consisting of: films, whether one-directional ortwo-directional films, and multilayer films with other polymericmaterials; films for use in the agricultural sector as mulching films;cling films (extensible films) for foodstuffs, for bales in theagricultural sector and for wrapping of refuse; shrink film; bags andsheathes for gathering organic matter packaging for foodstuffs bothsingle-layer and multilayer; coatings obtained with theextrusion-coating technique; multilayer laminates with layers of paper,plastic materials, aluminium, or metallized films; foamed or foamablebeads for the production of pieces formed by sintering; foamed andsemi-foamed products; foamed sheets, thermoformed sheets and containersobtained therefrom for the packaging of foodstuffs; containers ingeneral for fruit and vegetables; composites with gelatinized,destructurized and/or complexed starch, natural starch, flours, otherfillers of natural, vegetal or inorganic origin; and fibres, fabrics andnon-woven fabrics for the sector of health, sanitary products, andhygiene; which comprises shaping a polymeric composition according toclaim
 1. 18. Polymeric composition according to claim 2 wherein said atleast one other polymer (B) is a polymer of synthetic origin selectedfrom the group consisting of polylactic acid, poly-ε-caprolactone,polyhydroxybutyrates, such as polyhydroxybutyrate-valerate,polyhydroxybutyrate propanoate, polyhydroxybutyrate-hexanoate,polyhydroxybutyrate-decanoate, polyhydroxybutyrate-dodecanoate,polyhydroxybutyrate-hexadecanoate, polyhydroxybutyrate-octadecanoate,and polyalkylene succinates.
 19. Polymeric composition according toclaim 3 wherein said at least one other polymer (B) is a polymer ofsynthetic origin selected from the group consisting of polylactic acid,poly-ε-caprolactone, polyhydroxybutyrates, such aspolyhydroxybutyrate-valerate, polyhydroxybutyrate propanoate,polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decanoate,polyhydroxybutyrate-dodecanoate, polyhydroxybutyrate-hexadecanoate,polyhydroxybutyrate-octadecanoate, and polyalkylene succinates. 20.Polymeric composition according to claim 4 wherein said at least oneother polymer (B) is a polymer of synthetic origin selected from thegroup consisting of polylactic acid, poly-ε-caprolactone,polyhydroxybutyrates, such as polyhydroxybutyrate-valerate,polyhydroxybutyrate propanoate, polyhydroxybutyrate-hexanoate,polyhydroxybutyrate-decanoate, polyhydroxybutyrate-dodecanoate,polyhydroxybutyrate-hexadecanoate, polyhydroxybutyrate-octadecanoate,and polyalkylene succinates.